Production of dialiphatic tind dihalides



United States Patent 3,387,012 PRODUCTION OF DIALIPHATIC TIN DIHALIDES Wolfgang Jasching, 26a Richard-Wagner-Strasse, Konigsbrnnn, Germany, and Volker Franzen, 24 Panorama- Strasse, Heidelberg, Germany No Drawing. Filed Sept. 10, 1965, Ser. No. 486,564 Claims priority, application 2germany, Sept. 12, 1964,

8 Claims. (Cl. 260-429.7)

ABSTRACT OF THE DISCLOSURE Organotin halides are prepared by reacting at elevated temperature metallic tin with an aliphatic halide, whose hydrocarbon group contains 4 to 12 carbon atoms, in the presence of a catalyst of the formula MeX wherein Me is a member of the group consisting of arsenic and antimony, X is a halogen of the group consisting of chlorine, bromine, and iodine, and n is an integer corresponding to the valance of Me.

This invention relates to the production of alkyl tin halides.

At present, the commercial production of alkyl tin halides is carried out essentially according to two methods which both start from tin tetrachloride. The one method uses a Grignard compound as alkylating agent, the other method employs an aluminum alkyl compound. Both procedures follow the general equation Much work has been done to render said methods economic. Nonetheless, they are not fully satisfactory because the procedure remains rather complicated and expensive.

It is, therefore, a principal object of this invention to provide a simplified process for the preparation of alkyl tin halides and more particularly a process where the alkyl tin halide can be prepared in a single step.

It is another object of the invention to provide a process which does not require a metal organic alkylating agent.

Still another object of the invention is to provide a process for the preparation of alkyltin halides where relatively cheap metallic tin can be used as starting material instead of tin tetrachloride.

A further object of the invention is to provide a process for the preparation of alkyltin halides which does not involve the use of inflammable solvents whose recovery requires additional cost.

Some methods are known which allow to react metallic tin directly with alkyl halides to form alkyl tin halides. Such direct syntheses, however, have succeeded only with especially reactive alkyl halides, such as iodides and certain bromides, or with such alkyl halides where the halogen atom is structurally activated, for instance by double "ice bonds. Direct syntheses with alkyl chlorides, for instance those where the alkyl group contains more than 4 C atoms, could not be carried out commercially with commercially attractive yields.

Particularly, no method is known which allows of producing dihexyl, dioctyl, or didecyl tin dichloride from metallic tin and the respective alkyl chlorides with economic yields. It is just those higher alkyl tin chlorides which are important for the preparation of corresponding organotin compounds which are useful as stabilizers for halogen containing resins, particularly polyvinyl chloride. Such higher alkyl tin compounds, for instance the dioctyl tin compounds, are much less toxic than the corresponding methyl, ethyl, propyl and butyl compounds and are, therefore, increasing used as physiologically harmless stabilizers.

We have now found that dihydrocarbon tin dihalides can be prepared in good yields by direct reaction of metallic tin with alkyl or alkylene halides, or mixtures of different alkyl or alkylene halides, when the reaction is carried out in the presence of an arsenic or antimony halide, or mixtures thereof, in amounts of 1 to 8 mole percent, calculated on tin. The reaction proceeds in a single step according to the equation wherein X is halogen and R is alkyl. In this process, the principal reaction product is always dialkyltin dihalide. In addition, minor amounts of monoalkyltin trihalide and trialkyltin monohalide are formed. The process has particular commercial interest for the production of dialkyl and dialkylene tin dihalides where the hydrocarbon group contains 4-12 C atoms.

Suitable metal halide catalysts are particularly arsenic (III) chloride, arsenic (III) bromide, arsenic (III) iodide, antimony (III) chloride, antimony (III) bromide, and antimony (III) iodide. However, also the corresponding pentavalent halides can be employed, particularly those which decompose wholly or in part at reaction temperature to the trivalent compounds.

In some cases, the reaction can be still further accelerated when, in addition to said metal halides, a secondary catalyst is added to the reaction mixture. Such secondary catalysts are dialkyltin halides in a concentration of 2 to 6 mole percent, calculated on metallic tin; preferably, dialkyltin dihalides are used whose alkyl groups are identical with the alkyl groups of the desired end product.

For a fast termination of the reaction, it is of advantage to use an excess of the alkyl halide, whereby a mole ratio of tin to alkyl halide of 1:3.0-7.0 is preferably employed. If less reactive alkyl halides, for instance the higher alkyl chlorides having 6-12 carbon atoms, are employed, it may be of advantage to add a more reactive alkyl halide, whose amount may remain far below the stoichiometrically required amount. Suitable mixtures contain, for instance, tin, alkyl chloride, and as reactive addition alkyl iodide in the mole ratio of 1:3.0-7.0:0.1-0.4, or tin, alkyl chloride, and alkyl bromide in the mole ratio of 1:3.0-6.0:0.21.3.

Though a solvent is not required for the reaction, it may be added as a diluent to slow up the rate of reaction when particularly reactive alkyl halides are employed.

Our new process is essentially independent of the form and grain size of the tin employed. The reaction can be carried out not only with finely powdered tin but also with coarser powder or tin foil or even with turnings.

It is of advantage to carry out the reaction under exclusion of moisture or with removal of water since in this way the formation of decomposition products, e.g. inorganic tin compounds (SnC'l and of volatile hydrocarbons can be substantially prevented. Moisture is readily removed continuously by separating out water, which may have been introduced by the reactants or also gen erated during the reaction, continuously by an azeotropic reflux distillation.

Even when alkyl chlorides are used, the reaction time is surprisingly short. Depending on the kind and amount of the additives and the temperature, the required reaction time will be generally bet-ween 45 minutes and 6 hours. With the more reactive alkyl halides, for instance the bromides, the time may be still shorter.

The reaction is best carried out in the temperature range between 90 and 210 C.; these limits are, however, not critical and higher or lower temperatures may be used.

The reaction mixture can be processed in accordance with known methods, and the alkyltin halides can be purified, for instance, by distillation. The alkyl halide used in excess can be recovered almost completely by distillation. Similarly, alkyl iodide added to the alkyl chlorides is also recovered from the reaction mixture by distillation; as numerous tests have shown, 50-80 percent of the alkyl iodide remain unreacted in the reaction.

The monoalkyltin trihalides obtained as by-products are valuable intermediary products and can be used as starting materials for the preparation of auxiliary agents in the plastics production.

Compared with the conventional Grignard synthesis, the new process has the advantage of requiring much less time and apparative installations. Particularly, the new process makes it possible to use cheaper alkyl chlorides, e.g. those having more than 4 C atoms, which heretofore could not be reacted in a direct synthesis with economically satisfactory yields.

The following examples are given to illustrate but not to limit the invention. In all examples, the tin was employed in the form of a fine powder, maximum grain size 6-25u. The last example is added to show, in comparison, the unsatisfactory results obtained with the conventional Grignard method.

Example 1 A mixture of G. Sn 18.0 n-Octyl chloride 150.0 n-Octyl iodide 7.6 Antimony (III) iodide 6.0

was refluxed under stirring for 70 minutes at about 180 C. in a vessel provided with a water trap. Subsequently, the clear reaction solution, which did no longer contain any tin, was distilled. Thereby, 91.6 g. of excess n-octyl chloride and 5.4 g. unreacted n-octyl iodide were recovered. The distillation residue of 68 g. contained 41.2 g. of pure dioctyltin dichloride (65.5% of theory), 10.5 g. of pure monooctyltin trichloride (20% of theory), traces of trioctyltin monochloride, and some tin (II) chloride.

If the same mixture but without the antimony (III) iodide catalyst, was refluxed in the same manner, no tin had been reacted after 8 hours of heating at 180 C.

Example 2 Example 1 was repeated but the amount of catalyst was reduced to 1.8 antimony (III) chloride. After refluxing for 6 /2 hours, all the tin had been reacted, except a residue of 0.3 g. After distilling off the excess n-octyl chloride and n-octyl iodide, there remained a residue of 48.0 g. (Sn content 28.64%), which consisted essentially of dioctyltin dichloride and monooctyltin trichloride. The monooctyltin trichloride was distilled off, and the residue was saponified with ZnNaOI-I at 100 C. Thereby, 28.3 g. of dioctyltin oxide were obtained in a yield of 51.7 percent of theory (Sn content found 33.05%; calc. 32.85% The monooctyltin trichloride fraction was also saponified and yielded 8.9 g. of octylstannonic acid (Sn found 44.2%; lcalc. 44.9%). The antimony remained in the aqueous saponification liquor.

Example 3 Example '2 was repeated, with further addition of 2.0 g. of dioctyltin dichloride as auxiliary catalyst. The tin had reacted Within 4 hours, leaving a residue of 0.4 g. After distilling off the excess n-octylchloride, n-octyl iodide, and the monooctyltin trichloride, there was obtained a residue of 47.8 g. containing 3-8.0 g. of pure dioctyltin dichloride. Deducting the 2.0 g. of dioctyltin dichloride added as secondary catalyst, the obtained dioctyltin dichloride corresponded to a yield of 57% of theory.

Example 4 Example 2 was repeated with further addition of 2.5 g. of antimony (III) iodide. In this case, the tin had completely reacted already after 2 hours of refluxing at C. Distillation of the excess n-octylchloride, n-octyl iodide, and monooctyltin trichloride left a residue of 49.0 g. of crude dioctyltin dichloride. Saponification of the residue with sodium hydroxide produced 31.4 g. of dioctyltin oxide (Sn found 33.0%; calc. 32.85%), corresponding to a yield of 57.5% of theory.

Example 5 A mixture of G. Tin 18.0 n-Octyl bromide 190.0 Antimony (III) iodide 4.0

found 33.3%; calc. 32.8%).

Example 6 A mixture of G. Tin 18.0 n-Octylchloride 113.0 n-Octylbromide 30.0 Antimony (III) iodide 6.0

was refluxed under stirring in a vessel provided with a water separator at about 180 C. for a period of 45 minutes. After this time, the tin was completely consumed. The reaction mixture was processed as described in the preceding examples and yielding 30.8 g. of pure dioctyltin oxide.

Example 7 A mixture of G. Tin 18.0 Decylchloride 179.0 Decyliodide 12.0 Antimony (III) iodide 6.0

was heated with agitation for 4 hours at C. After that time, the tin had been consumed to a residue of 1.8 g. The reaction mixture was filtered and the filtrate was distilled in vacuo to remove excess decyl chloride, unreacted decyl iodide, and monodecyltin trichloride formed as by-product. As distillation residue, there were obtained 33 g. of crude didecyltin dichloride (Sn found 26.1%; calc. 25.2%).

Example 8 A mixture of G. Tin 18.0 Laurylchloride 211.0 Lauryliodide 13.5 Antimony (III) iodide 6.0

was heated with stirring for 4 hours at 210 C. Within this time, 14.5 g. of tin had been reacted. The reaction mixture was processed as described in the preceding examples; on saponification of the obtained crude dilauryltin dichloride, 23.5 g. of dilauryltin oxide (Sn found 24.8%; calc. 25.1%) were obtained.

Example 9 A mixture of G. Tin 12.0 n-Hexylchloride 81.2 n-hexyliodi-de 4.6 Antimony (III) iodide 2.6

was shaken in a pressure tube 6 hours at 180 C. Thereby, 2 g. of the tin remained unreacted. Processing the reaction mixture in the :manner described hereinbefore yielded 11 g. of pure dihexyltin oxide (Sn found 38.9%; calc. 39.0%

Example 10 A mixture of Tin 18.0 n-Hexylbromide 167.0 Antimony (III) iodide 4.0

was refluxed with stirring in a vessel equipped with a water trap for /2 hour at 156 C. The clear reaction solution was filtered from the tin residue (0.1 g.). The filtrate was processed as set forth in Example 2. On saponification of the crude dihexyltin dibromide, 37.5 g. of dihexyltin oxide, corresponding to a yield of 57.5 percent, were obtained.

Example 11 A mixture of Tin 18.0 1,4-dichloro-2-butene 45.0

Diethyleneglycol diethyl ether (dried over sodium) as diluent 200.0 Antimony (III) iodide 4.0

were heated 3 hours at 95 C. with stirring. Thereby, 16.7 g. of the tin had reacted. After filtration, the reaction mixture was distilled. The first run contained the unreacted dichlorobutene and the diethyleneglycol diethylether; subsequently, pure reaction product distilled over at 82-83 C. 0.05 mm. 33.6 g. of dibutenyl tin dichloride were obtained (Sn found 24.7%; calc. 31.5%).

was refluxed 5 hours at 102 C. Thereby, 6.5 g. (54.2%) of the tin reacted to form essentially dibutyl tin dibrotnide and some monobutyltin tribromide.

If the test was repeated without the antimony iodide, 11.9 g. of the tin had not yet reacted after 5 hours. In other Words, there was substantially no reaction.

Example 13 A mixture of G. Tin 18.0 n-Octylchloride 150.0 n-Octyliodide 7.6 Arsenic (III) bromide 2.5

was refluxed with stirring in a vessel equipped with a water trap. After 4 hours, the tin had completely reacted. On processing the reaction mixture as in the preceding examples, 31.1 g. of pure dioctyl tin oxide were obtained.

For purposes of comparison, a mixture similar to that used in Example 1 was reacted, which, however, contained instead of antimony iodide, in accordance with a known method, magnesium in the presence of an alcohol and an ether as catalyst. Said mixture consisted of 18 g. of tin, 67 g. of n-octylchloride, 4.3 g. of n-octyliodide, 2.7 g. of octanol, 12 g. of diethyleneglycol diethylether, and 0.18 g. of magnesium powder. It was refluxed 5 hours at 180 C. with stirring. After that time, the reaction mixture still contained 16 g. of unreacted tin and 1.5 g. of stannous chloride. Therefore, only 11.1 percent of the tin had reacted, part thereof with the formation of undesired inorganic tin compounds.

We claim:

1. A method for the production of organotin dihalides comprising reacting metallic tin at elevated temperature with an aliphatic halide, whose hydrocarbon group contains 4 to 12 carbon atoms, in the presence of a catalyst of the formula MeX wherein Me is a member of the group consisting of arsenic and antimony, X is a halogen of the group consisting of chlorine, bromine, and iodine, and n is an integer corresponding to the valence of Me.

2. The method as claimed in claim 1 wherein said catalyst is applied in an amount of l to 8 mole percent, calculated on tin.

3. The method as claimed in claim 1 wherein said catalyst is a compound of trivalent arsenic or antimony.

4. The method as claimed in claim 1 wherein the reaction is carried out at a temperature of to 210 C.

5. The method as claimed in claim 1 comprising adding to the reaction mixture as secondary catalyst a dihydrocarbon tin halide, whose hydrocarbon group is the same as that of said aliphatic haides, in an amount of about 2 to 6 mole percent, calculated on metallic tin.

6. The method as claimed in claim 5 wherein the reaction mixture contains tin, alkyl chloride or bromide, and alkyl iodide in the mole proportions 1:3.07.0:0.10.4.

7. The method as claimed in claim 5 wherein the reaction mixture contains tin, alkyl chloride, and alkyl bromide in the mole proportions 1:3.0-6.0:0.2l.3.

8. The method as claimed in claim 1 comprising continuously removing water from the reaction mixture during reaction.

References Cited UNITED STATES PATENTS 2,852,543 9/1958 Blitzer et al 260429.7 3,085,102 4/1963 Yatagai et al 260429.7

FOREIGN PATENTS 25,664 2/1963 Japan.

TOBIAS E. LEVOW, Primary Examiner.

W. F. W. BELLAMY, Assistant Examiner. 

